Stinging phacelia is a member of the water leaf family (Hydrophyllaceae). The family name is derived from the Greek words hydro (water)and phyllon (leaf). The waterleaf family consists of some 20 genera and around 300 species of mostly herbaceoussubshrubs. Members of the family occur throughout North and South America,central and southern Africa, Southeast Asia, and far eastern Russia. Othergenera in the waterleaf family include Pholistoma, Eucrypta, Emmenanthe (whispering bells), Nama (purple mat), Nemophila (baby blue eyes), and Eriodictyon (yerba santa). Members of the waterleaf family are noted for the value as ornamental plants. The family, which is most closely related to the phlox family (Polemoniaceae), does not include any particularly invasive species.

The genus Phacelia includes some 175 species found in the New World.The genus is especially well represented in western North America. California hosts 94 species and 29 subspecies, all of which are indigenous. San Francisco supports three species of Phacelia(P. californica, P. distans, P. malvifolia). The genus Phacelia derives its name from the Greek word phakelos (cluster) for the tightly coiled, one-sided clusters of flowers. Several species of Phacelia are valued garden plants, such as California desert bluebells, P. campanularia. The foliage of many has a pleasant fragrance, although some have a foul odor.Some members of the genus produce highly irritating hairs on the leaves and stems, which cause vesicular dermatitis. Although dermatologists report that dermatitis caused by stinging phacelia is similar to resembling that caused by poison oak, I find it more like stinging nettle (Urtica dioica – Urticaceae). The irritation is caused by compounds contained in pustules or glands at the base of the hairs.

Stingingphacelia is a branching herbaceous annual, reaching up to 3 feet high. Itproduces entire (not dissected) maple-shaped leaves similar to members of the mallow family (Malvaceae hence the species name). The leaves and stems aredensely covered with stiff yellow hairs. Flowers appear April through June and consist of tight clusters of small, white flowers in caterpillar-like coils.The stamens protrude noticeably beyond the petals.

Stingingphacelia occurs in moist sandy and gravelly places below 3500 feet in redwood forests, mixed evergreen forests, closed-cone pine forests and northern coastal scrub. It is distributed near the coast from San Luis Obispo County northward to Oregon, where it has possibly been extirpated. The species has been recorded in San Luis Obispo, Monterey, San Mateo, San Francisco, Marin, Sonoma(uncommon), Mendocino (rare), and Contra Costa counties. In San Francisco,stinging phacelia was recorded historically from Lobos Creek, Point Lobos,Laurel Hill Cemetery, Golden Gate Park, Lake Merced, Mt. Davidson, San MiguelHills, and Bayview Hills. It can still be found at Lobos Dunes, Sharp Park,Grandview Park, Glen Canyon, Strawberry Hill in Golden Gate Park, O’Shaugnessy Boulevard, and Yerba Buena Island. Nearby, it is also present on San Bruno Mountain, Angel Island, Montara Mountain, Pedro Point, and in the Crystal Springs watershed. The type specimen was collected by Chamisso in the Presidio in 1816.

Although the flowers are not particularly showy, stinging phacelia is an attractive spreading herb. Phacelias are a valuable source of nectar native wasps, flies,bee flies and ants, as well as honeybees. It would make a fine edge or filler plant for the garden, especially on our loose sandy soils. Just don’­t plant it too close to any pathways, remember its irritating properties when weeding around it, and be aware that it can become weedy when cultivated in sandy soils.